1. Field of the Invention
The present invention relates to an aqueous cleaning system and process, and more particularly, to an aqueous cleaning system and process for precision cleaning and testing of critical application gas systems including oxygen, nitrogen and hydrogen gas systems, critical application fluid systems, and cryogenic systems.
2. Discussion of the Prior Art
Surface vehicles, including military and commercial aircraft, and sub surface ships including military and commercial submarines, generally comprise oxygen, nitrogen and hydrogen gas systems. These gas systems must be cleaned and maintained in a clean condition according to predetermined standards. For example, military aircraft gas systems must meet certain well defined military standards for cleanliness as set forth in MIL-STD-1359. The gas systems are typically cleaned during routine maintenance cycles or between maintenance cycles if they are compromised through accidental contamination from water, fuels, lubricants, or any other foreign substance. Additionally, new components in the gas systems may also require cleaning prior to incorporation into the system. These components generally require cleaning because in a typical manufacturing process, such as machining, various substances are utilized to facilitate the process. For example, lubricants including cutting oil and grease are widely used in the machining process and leave a residue on the machined part. Manufacturing residues as well as other contaminants must be removed because of the potential dangers they pose; namely, health risks if the gas system is part of a breathing air system, and/or explosion risks since these gases are combustible or oxidizers.
Systems and processes for cleaning the above-described gas systems are well known and may be divided into two broad categories; namely, non-aqueous and aqueous. Cleaning systems and processes which fall into the non-aqueous category utilize specific chemicals to clean the gas systems or components thereof. Essentially, in a non-aqueous cleaning system and process, chemical agents may be flushed through the gas system for a given period of time at specific flow rates and pressures to remove the contaminants, or individual components comprising the gas systems may be submerged in tanks or vats containing the chemical agents to remove contaminants. The tanks or vats may be agitated to facilitate the cleaning process. Currently, certain chlorofluorocarbons are widely used as non-aqueous cleaners for cleaning gas systems or components thereof because of their excellent degreasing properties and the fact that they leave little or no residues. Two of the most common chlorofluorocarbons utilized today are trichlorotrifluoroethane (Freon-113.RTM.) and 1,1,1-trichloroethane (1,1,1-TCA). Both of these substances provide the high degree of cleaning required in the applications described above; however, these substances may pose a serious environmental threat. These substances are classified as Class I Ozone Depleting Substances (ODS), and depletion of the ozone layer may have profound detrimental consequences for the earth's inhabitants. The use and disposal of these hazardous substances are therefore governed under the strict standards of various international, federal, state, and local laws and regulations. Consequently, the potential harm from these substances along with the costs associated with the use of the substances, the taxes, and the disposal of these substances, which is approximately $7,500.00 for a 55 gallon drum, necessitate the need for alternative cleaning systems and processes. In addition, international, and federal laws will require the eventual phasing out of chlorofluorocarbon use.
Given the concerns associated with non-aqueous cleaning systems and processes, the use of aqueous cleaning systems and processes are becoming more prevalent. In aqueous cleaning systems and processes, water and various water soluble cleaning agents may be flushed through the gas system for a given period of time at specific flow rates to remove the contaminants, or individual components comprising the gas systems may be submerged in tanks or vats containing the water and water soluble cleaning agents to remove contaminants. The tanks or vats may be agitated to facilitate the cleaning process. The operation of the aqueous cleaning system is similar to that of the operation of the non-aqueous cleaning system and process described above; however, in the aqueous cleaning system and process, multiple flushing and rinsing cycles are necessary to achieve the same level of cleanliness as the non-aqueous cleaning system provides, thereby producing large quantities of waste water. In addition, while the water soluble cleaning agents themselves do not pose an environmental threat, the contaminants removed in the cleaning process typically do pose at least some environmental risks. Accordingly, similar to the disposal of the chemical waste discussed above, large quantities of waste water containing water soluble cleaning agents and contaminants must be treated in accordance with various federal, state and local laws and regulations before being returned to nearby waterways or to the ground water. Therefore, as with the case described above, cost may become the deciding factor.
Another problem associated with currently existing aqueous cleaning systems and processes is a lack of flexibility. Generally, currently existing aqueous cleaning systems are housed within large laboratory type environments. Consequently, remote cleaning, for example, on the flightline, is not possible. A typical situation where this problem might arise is in the case where a component or multiple components of a gas system needs to be replaced quickly on the flightline. The component or components may have been coated with a chemical to prevent corrosion during storage or while awaiting subsequent processing, and therefore may not have been cleaned initially. Accordingly, the component or components would have to be taken back to the laboratory for cleaning thereby contributing to aircraft downtime.